Modern aircraft typically have an inert gas generation-based fire and explosion prevention and/or suppression system. A system may also be known as an onboard inert gas generation system or “OBIGGS.” In an OBIGGS system, nitrogen enriched air (“NEA”) is mixing with air in a fuel tank. The mixture is commonly referred to as “ullage”. Oxygen concentrations are diluted so that in an event, like combat or upon the occurrence of a spark, in which fuel might tend to ignite combustion is unlikely. NEA introduced in a fuel tank must be adequately mixing with existing ullage so that the oxygen concentration throughout the tank is low enough to minimize a probability of combustion.
Fuel tanks for larger aircraft, such as a Boeing 747® aircraft, typically have a fuel tank boundary in which wing tanks and a center tank are disposed. Surge tanks are placed in the wings outboard of the wing tanks to capture any sloshing the fuel tank might encounter when carrying out maneuvers. The surge tanks are located outboard of the wing tanks and return the sloshed fuel to the wing tanks by gravity. The fuel tanks are exposed to ambient pressure and allow air into the tanks through the surge tanks.